Scheme for remote control of the output power of a transmitter in a smart sfp transceiver

ABSTRACT

A scheme is described for remote control of the output power of a transmitter in a smart SFP (or SFP+, or XFP) duplex (or BiDi, or SWBiDi) transceiver in a communication system using an operating system with OAM and PP functions, an OAM, PP &amp; Payload Processor, a transceiver, an optical power meter (optional), a BERT, and an optical link in the field.

FIELD

Embodiments of the invention relate to a scheme for remote control of anelectro-optical parameter of a smart transceiver in an optical fibercommunication system, and more particularly, to a scheme for remotecontrol of the output power of a transmitter in the smart transceiver.The applications of embodiments of the present invention include a smarttransceiver installed in communication systems without opticalamplifiers as well as optically amplified wavelength divisionmultiplexing (WDM) communication systems, for example, such as long-haultransmission networks, access networks of fiber to the x (FTTx), passiveoptical network (PON) networks, and wireless backhauls between a basestation and an antenna tower or a remote radio head (RRH), but notlimited only to these systems. A smart transceiver is an intelligenttransceiver which can execute Ethernet in the First Mile Operation,Administration, and Maintenance (EFM OAM) functions specified in IEEE802.3ah, including an electrical loopback configuration and theproprietary protocol (PP) functions. The type of the smart transceiverincludes a smart small form-factor pluggable (SFP) transceiver, a smartsmall form-factor pluggable plus (SFP+) transceiver, and a smart 10gigabit small form-factor pluggable (XFP) transceiver, and a Duplexsmart transceiver as well as a bidirectional (BiDi) smart transceiverand a single wavelength bidirectional (SWBiDi) smart transceiver.

BACKGROUND

Setting the output power of a transmitter in a transceiver at an optimumlevel is very desirable because it (1) helps to avoid the overloading ofa receiver, (2) provides the link optimization of an optically amplifiedWDM communication system, and (3) reduces power consumption. The optimumoutput power of the transmitter depends solely on each system in whichthe transceiver is operating. Here all the communication systems aregrouped as follows: (1) communication systems without opticalamplifiers, and (2) optically amplified WDM communication systems.

For the communication systems without optical amplifiers, it is not rarethat a service provider encounters occasions of deploying a transceiverwhose transmitter output power set by the transceiver supplier mightoverload the receiver at the other end of the communication system whenthe link loss is much smaller, for example, a very short span of thefiber link, than the typical link budget of the transceiver. To avoidthe overloading, an optical attenuator of fixed attenuation isfrequently inserted just before the receiver, which is an extraexpenditure.

On the other hand, when the link loss of the communication system is alittle bit bigger than expected, the service provider sometimes needs toincrease slightly the output power of the transmitter, for example, byaround 1 dB while the increase is within the limit of the specificationof the transmitter.

For the optically amplified WDM communication systems, it is a commonpractice to execute the optimization of the link composed of multipletransceivers running at different wavelengths, optical multiplexes(MUX's), optical amplifiers, link fibers, and optical demultiplexers(DEMUX's), through tuning of an individual channel transceiver.Particularly, the output power of the transmitter of each transceiver isoptimized/equalized such that one channel, for example, would notpredominantly determine the overall performance of the link with opticalamplifiers.

For the reduction of power consumption, setting the output power of thetransmitter at the optimum rather than at the higher output powertypically set at the factory of the transceiver supplier will reducesignificantly the power consumption of a communication system where manytransceivers are used through the accumulation in saving of small amountof power consumption of each transceiver; this will also reduce thepower consumption in cooling the communication system at the centraloffice (CO) of the service provider which effectively saves the capitalexpenditure (CAPEX) and operating expenditure (OPEX) of the serviceprovider; this will also prolong the life span of this communicationsystem, particularly the transmitter of the transceiver.

A transceiver will, in general, be benefitted when it is equipped withthe adjustability of the output power of a transmitter in thetransceiver as described above. Because (1) a communication systemconsists of, at least, two transceivers where the transmitter of onetransceiver is transmitting a signal to the receiver of anothertransceiver, and (2) the optimum output power of the transmitter dependssolely on each system in which the transceiver is operating, thecontrollability of the output power of the transmitter in onetransceiver by another transceiver will be a desirable feature. This isparticularly true if two transceivers are physically separated far awayfrom each other. In other words, a remote controllability of the outputpower of the transmitter of one transceiver by another transceiver willbe very valuable, considering the facts that (1) the adjustment of itsoutput power can be executed by the technician at the CO where all thenecessary test equipments are accessible easily and (2) anothertechnician does not have to be present simultaneously at the site of thetransceiver which is in need of adjustment of its output power; thiswill save a lot of capital and operating expenditures (CAPEX and OPEX)by the service provider/operator.

SUMMARY

According to embodiments of the present invention, a scheme of remotecontrol of an output power of a transmitter in a smart transceiver maycomprise a smart transceiver at a first end of the optical link, theoptical link, a transceiver, an OAM, PP & Payload processor, anoperating system with the OAM and the PP functions, an optical powermeter at a second end of the optical link (optional), and a Bit ErrorRate Tester (BERT). A PP similar to OAM protocol data unit (OAMPDU) ofEFM OAM is a message protocol of changing or monitoring the output powerof the transmitter in the smart transceiver.

According to embodiments of the present invention, a smart transceiverat a first end of the optical link can perform the EFM OAM and the PPfunctions in passive mode including the electrical loopback and the PPfunctions. The smart transceiver is equipped with (1) a circuitry whichcan adjust the output power of the transmitter and (2) a circuitry whichcan measure the Tx output power or the Tx bias current of thetransmitter in the smart transceiver upon receiving a commanding messagein a PP from the transceiver at a second end of the optical link. Thetype of the smart transceiver may be SFP, or SFP+, or XFP, and Duplex,or BiDi, or SWBiDi.

According to embodiments of the present invention, an optical link maycomprise an optical MUX, optical amplifier(s), optical fiber(s), and anoptical DEMUX.

According to embodiments of the present invention, a transceiver at asecond end of the optical link can perform the EFM OAM and the PP inactive mode. This transceiver can send out a commanding message of theadjustment or measurement of the output power of the transmitter in thesmart transceiver in a first end of the optical link using a PP.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of exampleand not limitation in the figures of the accompanying drawings, in whichlike references indicate similar elements.

FIG. 1 shows a configuration for a scheme of remote control of theoutput power of a transmitter in a smart duplex transceiver.

FIG. 2 shows a detail functional block diagram of a smart duplextransceiver.

FIG. 3 shows a procedure for the remote control of the output power of atransmitter in a smart duplex transceiver.

DETAILED DESCRIPTION

As shown in FIG. 1, a scheme of remote control of the output power of atransmitter in a smart transceiver includes an operating system with OAMand PP functions 100, an OAM, PP & Payload Processor 101, a duplextransceiver 102, a pair of optical fiber jumpers 103 and 108, an opticallink 104, a pair of optical fiber jumpers 105 and 107, and a smartduplex transceiver 106, an optical power meter 109 (optional) and a BERT110.

As shown in FIG. 2, a smart duplex transceiver includes an opticalreceiver 200, an electrical path 201, an OAM, PP & Payload Processor202, a Loopback circuit 203, an electrical path 204, a Tx output powercontrol circuit 205, electrical paths 206, 207, and 208, a Tx outputpower monitoring circuit 209, an electrical path 210, and an opticaltransmitter 211.

The following is a procedure, shown in FIG. 3, for the remote control ofthe output power of a transmitter in a smart duplex transceiver 106.

It is assumed, but not required, during this procedure that thetransmission is error free in either direction, from the transceiver 102to the smart transceiver 106, or from the smart transceiver 106 to thetransceiver 102, because the PP messages of controlling the transmitteroutput power are to be exchanged between transceivers 102 and 106. Thisis typically met since almost all the systems in service are designed torun in error free region with even an extra system margin of few dB.

Sometimes, a variable optical attenuator might be needed between theoutput of the transmitter in the transceiver 102 and the optical jumper103, as well as between the optical jumper 108 and the input of thereceiver in the transceiver 102, if the total link loss is very smalland the overloading of receivers of two transceivers 102 and 106 isexpected.

Sometimes, the transmission with default settings of the communicationsystem over the optical link 104 might not be error free. In this case,all the PP messages might need to be sent repeatedly to make sure thatthe PP messages are received correctly by the transceiver at thereceiving side.

Operation One

The following is the first operation 301. Therefore, it is necessary,first of all, to configure the smart duplex transceiver 106 in aloopback mode to find the BER with the current settings of thetransceiver. For this, a loopback OAM Protocol Data Unit (OAMPDU)generated at the operating system with OAM and PP functions 100 is sentto an OAM, PP & Payload Processor 101 where the loopback OAMPDU isencapsulated serially with the payload, if there is any. During thisperiod, disable the output from the BERT 110. The output is sent to thetransceiver 102 where the electrical signal of the loopback OAMPDUmessage is converted into an optical signal. Then the optical signal ofthe loopback message is transmitted through the optical jumper 103, theoptical link 104, an optical jumper 105, and arrives at the smart diplextransceiver 106.

The optical signal arrived at the smart duplex transceiver 109 is thenconverted into an electrical signal at the receiver 200. The electricalsignal is transmitted through the electrical path 201, and arrives at anOAM, PP & Payload Processor 202 where the loopback OAMPDU message isseparated and executed. Now only the remaining payload, if there is any,passes through the OAM, PP & Payload Processor 202, an electrical path207, and arrives at the optical transmitter 210 where the electricalpayload signal is converted into an optical signal.

The optical signal of the payload from the smart transceiver 106 istransmitted through an optical jumper 107, the optical link 104, anoptical jumper 108, and arrives at the transceiver 102 where the opticalsignal is converted into an electrical signal. The electrical signaltransmits to the OAM, PP & Payload Processor 101. This completes theconfiguration in the loopback mode.

Operation Two

The following is the second operation 302. Enable the output from theBERT 110 and a pseudo-random bit stream is sent out at the same datarate of the communication system to the OAM, PP & Payload Processor 101.During this transmission period, do not send out any OAMPDU's and PP'sin the data stream. This pseudo-random data signal will be transmittedthrough the path described above during the preparation of the loopbackmode and then will return to the error detector of the BERT for the BERmeasurement. Record the measured BER.

Operation Three

The following is the third operation 303. Disable the output of the BERT110.

Operation Four

The following is the fourth operation 304. Disable the loopbackconfiguration of the smart transceiver 106 using the operation (1) abovewith a disable loopback OAM Protocol Data Unit (OAMPDU).

Operation Five

The following is the fifth operation 305. Send an output power monitorPP message generated at the operating system with OAM and PP functions100 to the OAM, PP & Payload Processor 101. The output is sent to thetransceiver 102 where the electrical signal of the output power monitorPP message is converted into an optical signal. Then the optical signalof the output power monitor PP message is transmitted through theoptical jumper 103, the optical link 104, an optical jumper 105, andarrives at the smart duplex transceiver 106. This PP message is forrequesting the output power monitoring circuit 209 to measure the Txoutput power or the Tx bias current and then sending it to thetransceiver 102 in another PP message generated in the transceiver 106.

The optical signal arrived at the smart duplex transceiver 106 is thenconverted into an electrical signal at the receiver 200. The electricalsignal is transmitted through the electrical path 201, and arrives atthe OAM, PP & Payload Processor 202 where the output power monitor PPmessage is separated. An execution message of the output power monitorPP message is sent to the Tx output power monitor circuit 209 whichmeasures the output power of the transmitter 211 accordingly. Themeasured Tx output power or the measured Tx bias current is processed inthe OAM, PP & Payload Processor 202 and sent along the electrical path207 to the transmitter 211 with the payload where it is converted intoan optical signal.

The optical signal is transmitted through the optical jumper 107, theoptical link 104, and the optical jumper 107, and arrives at thereceiver of the transceiver 102 where the optical signal is convertedback into an electrical signal. This signal is processed at the OAM, PP& Processor 101, and the measured Tx output power or the measured Txbias current is read out at the Operating System w/OAM and PP Functions100. Record the Tx output power or the Tx bias current.

Operation Six

The following is the sixth operation 306. Measure the optical power outof the fiber jumper 108 using the Optical Power Meter 109 and record theoptical power if the optical link 104 does not include any opticalamplifiers.

Operation Seven

The following is the seventh operation 307. Send an output poweradjustment PP message, a message that sets the Tx output power at aspecified value, generated at the operating system with OAM and PPfunctions 100 to the OAM, PP & Payload Processor 101. The output is sentto the transceiver 102 where the electrical signal of the output poweradjustment PP message is converted into an optical signal. Then theoptical signal of the output power adjustment PP message is transmittedthrough the optical jumper 103, the optical link 104, an optical jumper105, and arrives at the smart diplex transceiver 106.

The optical signal arrived at the smart duplex transceiver 106 is thenconverted into an electrical signal at the receiver 200. The electricalsignal is transmitted through the electrical path 201, and arrives at anOAM, PP & Payload Processor 202 where the output power adjustment PPmessage is separated. An execution message of the output poweradjustment is sent to the Tx output power control circuit 205 whichadjusts the output power of the transmitter 211 accordingly.

Operation Eight

The following is the eighth operation 308. Repeat operation (5) to readout the Tx output power or the Tx bias current at the new setting.Record this.

Operation Nine

The following is the ninth operation 309. Repeat operation (7). Repeatoperation (5) and record the Tx output power. Check that the Tx outputpower is consistent with what was set or expected.

Operation Ten

The following is the tenth operation 310. Repeat operation (8) andoperation (9) if needed.

Operation Eleven

The following is the eleventh operation 311. Repeat operation (1) andoperation (2). Confirm if the measured BER is indeed what is expected.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention.The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

1-24. (canceled)
 25. An apparatus for remotely controlling output powerof a first transceiver in a communication system, the apparatuscomprising: one or more optical links; and a second transceiver coupledto the one or more optical links and configured to communicate with thefirst transceiver located at a remote location, wherein the secondtransceiver is configured to: send a monitoring message to the firsttransceiver over the one or more optical links; in response to themonitoring message, receive information from the first transceiver overthe one or more optical links, the information comprising data relatingto transmit an amount of output power or transmit bias current of thefirst transceiver; and send an adjustment message to the firsttransceiver over the one or more optical links for changing the amountof the transmit output power or transmit bias current of the firsttransceiver.
 26. The apparatus of claim 25, wherein the secondtransceiver is further configured to: send a first message to enable aloopback configuration mode of the first transceiver; send a test signalto the first transceiver in the loopback configuration mode; in responseto the test signal, receive a response signal from the firsttransceiver; measure bit error rate (BER) on the received responsesignal; and send a second message to disable the loopback configurationmode of the first transceiver.
 27. The apparatus of claim 26, whereinthe test signal comprises a pseudo-random data signal.
 28. The apparatusof claim 25, further comprising a power meter configured to measureoptical power on one or more fiber jumpers disposed between the one ormore optical links and the second transceiver.
 29. The apparatus ofclaim 25, wherein the first transceiver comprises a pluggabletransceiver or a small form-factor pluggable transceiver.
 30. Theapparatus of claim 29, wherein the small form-factor pluggabletransceiver comprises: a duplex small form-factor pluggable (SFP)transceiver, a bidirectional small form-factor pluggable (BiDi SFP)transceiver, a single wavelength bidirectional small form-factorpluggable (SWBiDi SFP) transceiver, a duplex small form-factor pluggableplus (SFP+) transceiver, a bidirectional small form-factor pluggableplus (BiDi SFP+) transceiver, a single wavelength bidirectional smallform-factor pluggable plus (SWBiDi SFP+) transceiver.
 31. The apparatusof claim 29, wherein the first transceiver is configured to support abit rate of at least one gigabits per second (Gps).
 32. A method ofremotely controlling a first transceiver in a communication system,comprising: receiving, at the first transceiver, a monitoring messageover one or more optical links from a second transceiver located at aremote location; in response to the received monitoring message,measuring transmit output power or transmit bias current of the firsttransceiver; sending to the second transceiver over the one or moreoptical links information relating to the measured transmit output poweror transmit bias current of the first transceiver; receiving anadjustment message over the one or more optical links from the secondtransceiver for adjusting the transmit output power or transmit biascurrent of the first transceiver; and adjusting the transmit outputpower or transmit bias current of the first transceiver, based on thereceived adjustment message from the second transceiver.
 33. The methodof claim 30, further comprising: receiving a message from the secondtransceiver to enable a loopback configuration mode of the firsttransceiver; and in response to the message, configuring the firsttransceiver to be in a loopback configuration mode.
 34. An apparatus inan optical communication system, comprising: one or more processorsconfigured to: receive a monitoring message over one or more opticallinks from a remote transceiver; in response to the received monitoringmessage, measure an amount of transmit output power or transmit biascurrent of the apparatus; send to the remote transceiver over the one ormore optical links information relating to the measured amount oftransmit output power or transmit bias current of the apparatus; receivean adjustment message over the one or more optical links from the remotetransceiver for changing the amount of transmit output power or transmitbias current of the apparatus; and adjust the transmit output power ortransmit bias current of the apparatus, based on the received adjustmentmessage from the remote transceiver.
 35. An electro-optical transceivercomprising: a processor; a monitoring transmit output power circuitcoupled to the processor and configured to measure an amount of transmitoutput power of the electro-optical transceiver; and a transmit outputcontrol circuit coupled to the processor and configured to control theamount of transmit output power of the electro-optical transceiver. 36.The electro-optical transceiver of claim 35, wherein the processor isconfigured to: receive a monitoring message for transmit output powerover one or more optical links from a remote transceiver; in response tothe received monitoring message, measure an amount of transmit outputpower of the electro-optical transceiver via the monitoring transmitoutput power circuit; and send to the remote transceiver over the one ormore optical links information relating to the measured amount oftransmit output power of the electro-optical transceiver.
 37. Theelectro-optical transceiver of claim 36, wherein the processor isfurther configured to: receive an adjustment message over the one ormore optical links from the remote transceiver for changing an amount ofthe transmit output power or transmit bias current of theelectro-optical transceiver; and adjust the amount of the transmitoutput power of the electro-optical transceiver, via the transmit outputcontrol circuit, based on the received adjustment message from theremote transceiver.